Hydroforming catalytic pentenes



United States Patent HYDROFORMING CATALYTIC PENTENES Robert C. Morbeck, Fanwood, N.J., assignor to Esso Research and Engineering Company, a corporation of Delaware Application March 1, 1955, Serial No. 491,477 4 Claims. (Cl. 20879) This invention relates to a process for improving the quality of light catalytic naphthas. The invention is direoted to the saturation of olefinic compounds in a particular selected fraction of a catalytically cracked naphtha. The invention provides a means for greatly improving the Motor Method octane rating of such catalytic naphtha fractions.

The invention involves fractionation of a catalytically cracked naphtha into at least two fractions, one of which constitutes the portion of the naphtha boiling in the range of about 65 to 115 F. Hydrogenation of this particular fraction in a hydroforming zone in admixture with conventional hydroforming feed provides substantial and unexpected advantages as regards the quality of the resultant hydrogenation products and the conduct of the hydroforming process. The invention is based on the discovery that the fraction of a catalytic naphtha boiling in the range of about 65 to 115 E; that is, the pentene fraction, is particularly susceptible to improvement in anti-knock quality under hydroforming conditions.

' transmissions has also aggravated the problem of satis-- It is known that hydrogenation of cracked naphthas ordinarily results in degradation in the anti-knock quality of the naphtha as evidenced by a substantial loss in the Research octane rating and very little, if any, improvement in the Motor Method octane rating. Unexpectedly, however, by hydrogenating the fraction of a catalytic naphtha boiling in the range of 65 to 115 F., it is possible to secure great improvements in-the Motor Method octane rating of this'particular fraction accompanied by little, if any, loss in the Research Method octane rating. It is the basic concept of thisinvention therefore, to hydrogenate this fraction in a hydroforming zone so as to upgrade the anti-knock quality of this specific fraction of a catalytic naphtha which is separated from the naphtha for this treatment.

It is a particular feature of this invention to carry out this treatment by admixing the catalytic pentene fraction with conventional hydroforming feed stock. This admixture is particularly suitable for use in a hydroforming process since the exothermic olefin saturation resulting provides a desirable source of heat for the endothermic reactions occurring during hydroforming of the conventional hydroforming feed stock.

In a specific embodiment of the present invention, a catalytic naphtha is divided into the pentene fraction and a heavier naphtha fraction and both of these, fractions are subjected to difienent and. specific hydrogenation conditions. By this means it is possible to upgrade the total catalytic naphtha by a hydrogenation treatment toobt'am results which cannot be achieved by hydrogenation of the total naphtha.

' The pentene fraction of a catalytic naphthajb oiling the: range of 65F. to 115' F., typically constitutes about60% of unsattirated, oIefinic compounds and of' saturated parafiins. More particularly, a typical pentene fraction of catalytic naphtha will constitute the following compositions:

Percent Branched olefins 36 Normal olefins 23 Cyclic olefins 1 Isoparaflins 38 Normal paraflins 2. The specific proportions of these constituents will of course vary somewhat in accordance with variations in the conditions of catalytic cracking and the feed stock employed. Pentene fractions adaptable to treatment by the present invention may, however, be characterized as constituting at least about unsaturated hydrocarbons.

The invention will be fully identified in the description which follows, and with reference to the accome' panying drawing which diagrammatically illustrates aflow plan of a specific and preferred embodiment of the invention.

One of the most important requirements of a high having such high compression ratios require use of high anti-knock gasolines. The more extended use of automatic fying the octane requirements of current :automotive engines. primarily been determined by the so-called Research Method, which can be determined by ASTM test, designated D908-47T. While this is an important and valuable anti-knock rating test, it has become appreciated that knocking tendency of a fuel in road performance is greatest during maximum load. It is therefore appreciated at this time that the Research octane number rating of a gasoline is not a complete indication of the value of a gasoline in satisfying an engine under road conditions,

As a result, other methods of determining octane ratings are commonly employed. One such method is the so-called Motor Method test, designated by ASTM Test Method D357-47. It has been found that the Motor Method octane determination correlates with the road per-. formance of a gasoline somewhat better than the Research octane rating.

In view of these basic factors, production of present day, high quality gasolines must be carried out with reference to both the Research and Motor Method octane rating. The over-all octane rating of the fuel is some function of. both. of these octane rating methods and can be approximated by averaging the Research and Motor Method ratings.

It is the principal object of this invention to provide a refining process particularly adapted for improving the Motor Method octane rating of naphthas. This inven-v tion therefore provides a valuable tool for providing higher quality gasolines in a manner heretofore unobtainable.

preciated by reference to Table 1, showing data obtained In the past, octane ratings of gasolines have The nature and benefits of this invention can be ap-.

by hydrogenating selected fractions of a light catalytic naphtha as compared to hydrogenation of the total light naphtha. In one of the hydrogenation operations employed, conditions were adjusted to secure essentially complete saturation of olefinic hydrocarbons present in the feed stock. This was achieved by treating the .naphtha feed stock at a temperature of 7.QF., a pressure of 2.00 .p.s.i.g., at a throughput of 1.7 v./v./hr., in the presence of 1500 s.c.f./b. of hydrogen in contact with a cobalt molybdate on alumina catalyst Under :these hydrogenation conditions, approximately 98% of the olefins present in the feed were saturated. In the other hydrogenation operation employed, using the same catalyst at the same temperature and with the same amount of hydrogen, and at throughputs of about 1.5 to 2 -v./v./-hr., pressure was maintained at the lower figure of 50-p.s.i.g., so as to cause partial saturation of the olefins present in the feed. Under these conditions, approximately 43% of the olefins were hydrogenated to saturation.

In the conduct of these experiments, three types of naphtha feed stock were employed. The first of these constituted the whole of a light catalytic naphtha boiling inthe range of about 65 F. to 363 F. A second fraction constituted only that portion of this naphtha boiling in the range of about 115 to 150 F. Finally, a third hydrogenation feed stock constituted only the pentene fraction of the light catalytic naphtha boiling in the range of about 65 to 115 F. The results of applying these hydrogenation treatments to these feed stocks under theh conditions specified are shown in Table I.

TABLE I genation conditions. The partial saturation hydrogenation treatment, when applied to only the pentene fraction of the naphtha again showed substantial advantages over treatment of the total naphtha. Thus, the partial saturation treatment of the pentene fraction resulted in a gain of 7 octane units by the Motor Method and of one octane unit by the Research Method. The data of Table I therefore, show the substantial and unexpected advantages of segregating the pentene fraction from a catalytic naphtha and applying a hydrogenation treatment to this specific fraction. By so doing, it becomes possible to greatly improve the Motor octane rating of this specific fraction while avoiding the degradation in Research octane rating otherwise resulting from hydrogenation of the total catalytic naphtha.

With reference to the hydrogenation of the intermediate naphtha fraction boiling within the range of 115 to 150 F., the data of Table I again show that this fraction cannot be appreciably upgraded in octane characteristics. Thus, because of loss in the Research octane rating, hydrogenation ,of this fraction at either partial or complete saturation conditions provides substantially no better result than treatment of the total naphtha. This data therefore establishes that hydrogenation of the pentene fraction of a catalytic naphtha by itself provides significant and unexpected improvement in anti-knock characteristics not obtainable by hydrogenating the total naphtha or narrow fractions of the naphtha other than the pentene fraction.

As formerly stated, the over-all octane rating of agaso- Hydrogenation of light catalytic naphtha Complete saturation Partial Saturation Olefin saturation, percent... Boiling range, FVT Vol. percent on total naphth Octsinle change (3 cc. TEL):

98 98 115/150 05/363 FER.-- 17 100 Referring to Table I, it will be observed that hydrogenation of the total naphtha conducted to secure complete saturation of olefins present, resulted in a substantial drop in the Research octane rating of the gasoline. This hydrogenation treatment resulted in a loss of 7 Research octane numbers. The operation caused a small improvement in the Motor octane rating of the gasoline amounting to 4.5 octane units. However, it is apparent that the-substantial loss in Research octane number would ordinarily far ofliset any value obtained by appreciation of'the small gain in Motor octane number. When treating the total naphtha under the milder hydrogenation conditions, causing partial saturation of olefins present, a smaller loss in Research octane resulted, although'in this case the Motor octane rating of the hydrogenated naphtha improved but little. Again, therefore, application of this hydrogenation treatment to the total naphtha is shown to be of little or no value so far as improving the overall octane quality of the gasoline.

As opposed to this, the data of Table I shows the substantial and unexpected improvement in the anti-knock quality obtainable when applying these same hydrogena tion conditions only to the pentene fraction of the naphtha. In particular, the data show thatin the complete saturation hydrogenation treatment applied to the pentene fraction of the naphtha, it was possible to increase the Motor method octane rating of this fraction by 14 units. Concomitantly, there was little change in the Research rating of the pentene fraction amounting only to'a decrease of 1.5 units which was substantially less than that resulting from treating the total naphtha under the same.hydro-.

line is best indicated by a consideration of both the Re search and 'Motor Method octane rating. To weigh in this consideration net octane change is'indicated in Table I which is simply the sum of the Research and Motor Method octane changes resulting from hydrogenation .of the different stocks. The unexpected and substantial advantage of hydrogenating the pentene fraction alone is particularly indicated by the net octane change data.

The remarkable increase in the Motor octane rating of the pentene fraction obtainable by hydrogenation is primarily due to the increased :lead susceptibility of the hydrogenated pentenes. Data-establishing this are, shown in Table II.

Table 11 Motor octane number Feed Saturated A product Leaded (3 M1. TEL) --86.0 99.9 +13.9 Clear 81.2 v 82.1 +0.9

A due to +1. 8 +17. 8

These datashow that while the clear octane number of the hydrogenated pentene. fraction is but little better than that of the unhydrogenated fraction, remarkably, the leaded Motor octane number attributable to the presence of tetra-ethyl-lead is increased by 17.8 octane An important feature of this invention is the manner in, hydrogen is conserved while achieving improvement in anti-knock quality. A catalytic naphtha contains a substantial amount of olefinic constituents resulting in high hydrogen consumptions when such naphthas are hydrogenated. For example, when hydrogenating a total light catalytic naphtha boiling in the range of about 65 to 363 F., a hydrogen consumption of about 500 to 600 standard cubic feet per barrel is required. From an economic viewpoint, this substantial consumption of hydrogen could not be justified for attaining the relatively insignificant change in anti-knock characteristics shown in Table I. However, by hydrogenating only the pentene fraction of a catalytic naphtha, while about the same amount of hydrogen is required per barrel of pentene feed, over-all hydrogen requirements are only a fraction of those required for treating the total naphtha. This can be appreciated by the fact that approximately a 2.0 Motor octane gain per 100 standard cubic feet of hydrogen per barrel can be achieved by treating the pentene fraction while the Motor Method octane gain in treating the total naphtha with the same amount of hydrogen is only about 0.5. Consequently, in. considering the hydrogenation of catalytic pentenes in accordance with this invention, as opposed to hydrogenation of other fractions of a catalytic naphtha, it is apparent that this invention provides a remarkable improvement in anti-knock quality for quantity of hydrogen required.

The data of Table I, show that partial saturation of the pentene fraction attains about half the improvement in Motor octane number which can be obtained by total saturation. These data are particularly significant in considering makeup of a refinery gasoline pool. Olefinic constituentshave a more desirable octane blending facfor than paraflinic constituents, and for this reason by partially saturating the pentene fraction as shown in Table I, the over-all effect in a gasoline pool is substantially'that obtainable by complete saturation of the pentene fraction. For this reason it is attractive in the practice of this invention to partially saturate rather than to completely saturate the pentene fraction of a light catalytic naphtha so as to further conserve hydrogen consumption and to provide a pool gasoline product of substantially the octane characteristics obtainable by other processes requiring greater amounts of hydrogen. In this connection it is generally preferred to saturate about 30% to 60%, for example, about 40% of the olefins present in the pentene fraction.

The desired hydrogenation of the catalytic pentene fraction is carried out in accordance with this invention by admixing the pentene fraction with conventional hydroforming feed stock and subjecting this mixture to conventional hydroforming treatment. As used herein, the term hydroforming is defined as an operation in which a petroleum naphtha is contacted at elevated temperatures and pressures and in the presence of added hydrogen with a solid catalytic material under conditions such that there is no net consumption of hydrogen. In the hydroforming operation it is necessary for best results to utilize a feed stock containing a substantial quantity of naphthenic hydrocarbons, say from about 35 to 50 volume percent, and usually the feed stock boils substantially within the range of from about 200 to 350 F. The light ends, in other words, the material boiling from about to 200 F. is not subjected to this reaction, for the reasons that the virgin naphtha light ends have a fairly good octane rating and that the materials boiling in this range when subjected to hydroforming produce an inordinately large amount of coke. However, in this invention, the catalytic pentene fraction is admixed with conventional hydroforming feed of the character identified. It is preferred to combine the catalytic pentenes with the virgin naphtha so as to provide a molal ratio of cracked olefins to naphthenes in the feed of about 0.5 to 2.0. Hydrogenation of these olefins in the hydroforming process releases heat in situ, thus supplying a subv VII and VIII of the periodic system of elements alone,

or generally supported on a base or spacing agent such as alumina gel, precipitated alumina or zinc aluminate spinel. Of these catalysts, a particularly effective hydroforming catalyst is one containing about 10 Weight percent molybdenum oxide upon an aluminum oxide base prepared by heat treating a hydrated aluminum oxide or upon a zinc aluminate spinel. The catalyst employed in hydroforming may also constitute a platinum group metal, preferably platinum itself, supported on one of the bases identified. The preferred catalyst of this type contains 0.05 to 2.0 weight percent of platinum supported on activated alumina, preferably eta alumina.

The hydroforming process may be conducted in any desired manner including fixed bed, moving bed, suspensoid, or fluidized solids operation and may be of the regenerative or non-regenerative type. However, in the example which follows, reference will be made particularly to a fluidized type of hydroforming. In this method of conducting hydroforming, the naphtha feed is contacted with a dense fluidized catalyst mass in a fluidized solids reactor system. The naphtha vapors are passed continuously through the dense, fluidized bed of hydroforming catalyst particles in a reaction zone, spent catalyst particles being withdrawn from the dense bed in the reaction zone and passed to a separate regeneration zone where inactivating carbonaceous deposits are removed by combustion, after which the regenerated catalyst particles are returned to the main reactor vessel. The catalyst particles, for proper fluidization, should be between about 200 and 400 mesh or about 10 to 200 microns in diameter, with a major proportion between about 20 and microns.

Specific hydroforming conditions which may be used in the practice of this invention are as follows:

The catalytic pentene fraction may be admixed with the hydroforming feed or may be separately brought into the hydroforming zone. The latter expedient is particularly desirable to permit control of the point at which the heat contribution of the olefin saturation is made available. Again, this perrnits maintaining the pentene fraction in the hydroforming zone for a shorter period than the remainder of the hydroforming feed. In this Way partial saturation, rather than complete saturation of the olefins of the pentene fraction may be achieved.

It is desirable in the practice of this invention to particularly treat the portion of the naphtha remaining after separation of the pentene fraction. It is particularly desirable to treat the heavier fraction of the catalytic naphtha by a hydrofining operation conducted at hydrogenation conditions different from those applied to the pentene fraction. This is achieved by hydrofining the heavier fraction of catalytic naphtha boiling in the range of about to 350 F. under conditions to secure a bromine number reduction of no more than about 20%. This results in primarily improving the engine cleanliness and stability characteristics of this naphtha fraction while contributing a sulfur reduction of about :one-third. Such hydrofining can be carried out using a hydrogenation .catalyst such as cobalt .molybdate at temperatures of about 400v to 700 F., at a pressure 'in the range of 50 to 250 pounds per square inch, throughputs of about 1 to 20 v./v./.hr., and at .hydrogen consumptions less than .60 standard cubic feet per barrel.

Referring now to .the drawing, a specific embodiment of this invention is illustratedshowing a specific example of the practice of this invention.

As illustrated, a gas oil feed stock boiling in the range of about 400 to 1100 F., forexample, may be brough into [catalytic cracking zone 1 through line 2. Catalytic cracking of a conventional nature will be carried out in zone 1 permitting removal of cracked products through line 3 for introduction to fractionation zone 4. Light gaseous products including C and lighter hydrocarbons may be withdrawn from fractionation zone 4 through an overhead line '5. A fraction including the catalytic naphtha fraction boiling in the range of about 50 to 400 F., may be removed through line 6. Higher boiling cracked products will be recovered from the fractionation zone through lower withdrawal lines 7 andS, etc.

The catalytic naphtha fraction may be passed to a secondary fractionation system 9, which may be operated to permit removal of residual amounts of C and lighter constituents through overhead line 10. In accordance with this invention, a sidestream is taken from fractionator 9 through line .11 constituting the pentene fraction boiling in the range of about 65 to 115 F. Preferably, a higher boiling fraction, boiling in the range of about 115 to 250 F. is withdrawn as a sidestream through line 22. Finally, a fraction boiling in the range of about 250 to 400 F. will be removed as a bottoms product through line 12.

The pentene fraction of line 11 is then passed to hydroforming zone 14. Virgin naphtha or other hydroforrning feed of the nature identified hereinbefore may be introduced through line 27 for admixture with the catalytic pentene fraction and for introduction to the hydroforming zone. Hydroforming is carried out in zone 14 under the conditions identified hereinbefore to achieve an olefin saturation which is preferably about 40% or greater and will generally be substantially 100%. The hydroformer product may then be passed through line 15 to zone 23 for caustic or water washing although this .is an optional step. Thereafter, the hydroforrned naphtha is passed to storage zone 17 through line 16 for blending with other gasoline blending stocks.

In the preferred conduct of this invention, the naphtha fraction of line 22'is passed directly to storage zone 17. This fraction requires no treatment except optional treatment for sulfur removal. If desired, however, the naphtha of line 22 may be combined with the naphtha of line 12 for treatment in hydrofining zone 18. In all .cases, the heavy naphtha fraction of line .12 issubjected to the hydrofining conditions identified hereinbefore. The hy drogenatedproduct from zone 18 is then passed into the storage zone .17 through line 20. The resultant blend of the productsof'lines 16, '22 and 20 constitutes a desirable high quality gasoline. ,It is apparent of course that other gasoline blending stocks may also be mixed with these constituents as desirable in conventional refinery practice.

What is claimed is:

1. A process for improving the anti-knock characteristics of a catalytic naphtha in which the pentene fraction of the said naphtha boiling in the range of about F. to 115 F., is segregated from the naphtha and admixed with feed to a hydroforrning process, said mixture being hydroformed to secure an olefin saturation of about 30% to 2. The process defined in claim 1 in which the feed to the hydroforming process is a virgin naphtha boiling in the range of about 200 to 350 F. and contains from 35 to 50 volume percent naphthenes and the hydroforming is conducted at a temperature of about 875 to 950 F.

and at a pressure of about 50 to 500 psi.

3. A process for upgrading catalytic naphtha compris ing the steps of fractionating the said naphtha to segregate a first fraction boiling below 65, a second-pentene fraction boiling in the range of about 65 to F., a third fraction boiling ,in the range of 115 -250 F. and a fourth fraction boiling above 250" F., mixing a virgin naphtha with the said second fraction and subjecting the mixture to hydroforming in the presence of a hydroforming catalyst under hydroforming conditions whereby said second fraction'is saturated to the extent of at least 30%, hydrogenating said fourth fraction to secure a bromine number reductionof about 20% and blending the hydroformed product with said third fraction and said treated fourth fraction to provide a naphtha product.

4. The method set forth in claim 3 in which the pentene saturation amounts to 3060%. I

References Cited in the file'of this patent UNITED STATES PATENTS OTHER REFERENCES 7 Haensel: Petroleum Processing,.April 1950, pp.'356- 

1. A PROCESS FOR IMPROVING THE ANTI-KNOCK CHARACTERISTICS OF A CATALYTIC NAPTHA IN WHICH THE PENTENE FRACTION OF THE SAID NAPHTHA BOILING IN THE RANGE OF ABOUT 65* F. TO 115* F., IS SEGREGATED FROM THE NAPHTHA AND ADMIXED WITH FEED TO A HYDROFORMING PROCESS, SAID MIXTURE BEING HYDROFORMED TO SECURE AN OLEFIN SATURATION OF ABOUT 30% TO 100%. 